Method of manufacturing a sintered silicon carbide ceramic part

Claim 1

A method of manufacturing a sintered silicon carbide part, the method comprising the following steps: (a) mixing a silicon carbide powder, at least one sintering additive, and an injection moulding agent; said sintering additive being chosen from the group consisting of boron, boron compounds, beryllium, beryllium compounds, aluminium and aluminium compounds; and said injection moulding agent comprising a mixture of polystyrene and a wax having a lower volatilisation temperature than the volatilisation temperature of the polystyrene, said polystyrene being provided in a quantity sufficient to be carbonized during sintering to produce 0.5% to 5% by weight of carbon relative to the weight of the silicon carbide; (b) forming a shaped part by injection moulding said mixture; (c) baking the moulded part in an oxidizing atmosphere to a temperature of 230° C. to 330° C. and then maintaining the part at said temperature for long enough to eliminate the wax and to reticulate and to oxidize at least a portion of the polystyrene; (d) heat treating the baked part in an inert atmosphere or in a vacuum by heating up to a final temperature of about 900° C., the temperature rising at a rate of between 50° C. per hour and 100° C. per hour such that the loss of weight of the part is stabilized when it reaches the final temperature; and (e) sintering the heat treated moulded part at a temperature of 1900° C. to 2200° C. in an inert atmosphere or under a vacuum.

Claim 2

A method of manufacturing a sintered silicon carbide part, the method comprising the following steps: (a) mixing a silicon carbide powder, at least one sintering additive, and an injection moulding agent; said sintering additive being chosen from the group consisting of boron, boron compounds, beryllium, beryllium compounds, aluminium and aluminium compounds; and said injection moulding agent comprising a mixture of polystyrene and a wax having a lower volatilisation temperature than the volatilisation temperature of the polystyrene, said polystyrene being provided in a quantity sufficient to be carbonized during sintering to produce 0.5% to 5% by weight of carbon relative to the weight of the silicon carbide; (b) forming a shaped part by injection moulding said mixture; (c) baking the moulded part in an oxidizing atmosphere to a temperature of 230° C. to 330° C. and then maintaining the part at said temperature for long enough to eliminate the wax and to reticulate and to oxidize at least a portion of the polystyrene; (d) heat treating the baked part in an inert atmosphere or in a vacuum by heating up to a final temperature of about 900° C., the temperature rising at a rate of between 50° C. per hour and 100° C. per hour such that the loss of weight of the part is stabilized when it reaches the final temperature; and (e) sintering the heat treated moulded part at a temperature of 1900° C. to 2200° C. in an inert atmosphere or under a vacuum.